This doesn't directly answer your question, but how I have my verify.txt might help you and others. At the bottom are the only fields that are available to use at this time. I pulled the fields from the compiled boxtrapper executable.

verify.txt template

Code:

To: %email%
Subject: Sender Verification Request [ verify#%msgid% ]
In the war on spam, here's another line of defense.
Your e-mail entitled "%subject%" to %acct% is from an e-mail address that I don't recognize yet. For me to recieve messages from your %email% address, please reply to this message without changing the subject.
Once you reply to this message, I'll get your original and future messages without further interference given that they're coming from %email%.
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%acct%
%msgid%
%subject%
%email%
%headers%
%webdomain%